The man who crashed to earth in a south-west London suburb on Sunday made his doomed attempt to stow away to Heathrow on a British Airways plane flying from Luanda, the Angolan capital, flight data records and a handful of money suggest.

What hopes, or fears, led him to clutch at the possibility of surviving a flight from Africa hidden in the landing gear of a plane may forever remain a mystery. While police are officially treating the death as unexplained, the key line of inquiry is that the man found at 7.40am across the pavement of Portman Avenue, East Sheen in affluent Richmond upon Thames, started his journey in the undercarriage of a British Airways Boeing 777 as it prepared to take off from the south Atlantic coast ofAfrica just before midnight.

Identification would prove difficult even without the impact of a fall from 2,000ft. Police have little to go on bar the handful of kwanza notes, the Angolan currency, found with the young man, thought to be in his 20s. He was dressed in a grey hoodie, jeans and trainers.

Almost certainly, he would have died long before flight BA76 travelled the more than 4,000 miles to London. His body fell as the wheels were lowered ready to land. He appears to be the second stowaway to perish on a BA flight from Africa in a little over two weeks – breaches of airline security that have experts questioning whether the consequences could have been far worse. The other, still unidentified man was discovered at Heathrow in August on a flight from Cape Town.

BA insists security is the airports' responsibility, and underlines that there has been "no confirmation that this incident is specifically connected to a British Airways aircraft". A spokesman added: "We are in contact with the Metropolitan police and looking at things in Luanda."

Flight records uncovered by the Guardian show that flight BA76 from the Angolan capital was on its final descent over west London between 7.40am and a final recorded arrival time at the gate of 7.58am, half an hour ahead of schedule.

Stowaways risk being crushed or burned by the wheels as soon as they are retracted after takeoff. At cruising altitudes of over 35,000ft, in the unpressurised wheel well, oxygen deprivation can kill. With temperatures plunging to -55C, stowaways would die of hypothermia.

Records collated by the US Federal Aviation Authority suggest that at best one in four stowaways survives, but many others die or fall in transit. Survivors rarely escape unscathed – frostbite claims limbs. Among the few who did live was a Romanian on a Vienna to Heathrow flight in 2010, but he was in the air for only an hour at an unusually low altitude; overnight from Africa is a death sentence.

There have been other dead bodies found in south-west London: in 2001, a stowaway from Pakistan fell into the car park of a Homebase store, not far from East Sheen, somehow causing no more casualties on the ground below.

For the man who died on Sunday, a few small bunches of flowers where his body landed is the only makeshift memorial. Residents on Friday expressed sympathy – and concern that it could happen again. Jamie Kugele witnessed the aftermath outside his house. "It was horrendous, he had massive trauma to his head. Forensics were everywhere. They kept looking up at the sky, and then I realised what had happened. You wonder what must be going through their [the stowaways'] minds."

At Luanda's Quatro de Fevereiro airport, sprawling slum housing runs right up to the perimeter fence. In these bairros, lacking basic services such as water and electricity, there are few tarred roads, houses are mostly self-built. Unemployment and crime rates are high.

For passengers in the international terminal, security is tight. Uniformed officers ask travellers to present documents perhaps 15 times before boarding aircraft. The airport is linked by internal roads to the domestic and military terminals where security is known to be more relaxed. Two BA flights a week carry mostly oil workers and Angolan students to the UK; economy return fares start at £1000, twice the average wage. The aircraft lands in Luanda at 5am on Saturdays and sits on the tarmac until the return at midnight, giving potential stowaways time and the cover of darkness.

While Angola's civil war has long ended, and domestic repression eased, poverty is rife. Despite being hailed as an economic success story, Angola admits that nine out of 10 people live in "inappropriate conditions". A widening rich-poor divide has increased anger and desperation.

Refugees from the Congo also turn up in Angola as in South Africa – the place many Angolans think of as being paved with gold. Yet here too the gap between rich and poor is keenly felt. Not far from Cape Town's international airport are notorious townships, including Gugulethu and Khayelitsha. The gleaming new terminal, rebuilt for the 2010 World Cup, is incongruous next to miles of straggling shack settlements from where, apparently, a man scaled the airport's perimeter fence on 22 August before hitching his fateful ride on the BA plane to Heathrow.

An airport spokeswoman said it had now tightened security to have all international flights followed by a security patrol vehicle after dusk, with a clear line of sight of the undercarriage of the aircraft.

Philip Baum, editor of Aviation Security International – who lives in East Sheen – said he was astonished there was not more shock and awe in the industry at the breaches of security: "If anybody from outside the airfield can climb into the aircraft, they can potentially secrete something far worse. If we're not detecting human beings, we're not necessarily going to find an improvised explosive device, which can be as small as a radio.

"We put so much focus on passenger screening and hi-tech explosive detection, but if the airfield itself is porous all that is meaningless."

BA said it employs security on the stand, people checking cargo and baggage holds, as well as vehicles following aircraft taxiing to the runways in both Luanda and Cape Town, with pre-flight checks that include the wheel well.